Washington: US President Donald Trump has told reporters that he likes Taylor Swift's music "about 25 per cent less now" that she endorsed a Democrat in a Senate race in Tennessee.

Swift on Sunday showed her political stripes in a post on Instagram in which she said she would be voting for Phil Bredesen for Senate, reports variety.com.

She wrote of the hotly contested Senate race that "as much as I have in the past and would like to continue voting for women in office, I cannot support Marsha Blackburn. Her voting record in Congress appalls and terrifies me." Blackburn is Bredesen's Republican opponent.

"I'm sure Taylor Swift doesn't know anything about her," Trump said on Monday. "Let's say that I like Taylor's music about 25 per cent less now."

Swift wrote that Blackburn "voted against equal pay for women. She voted against the Reauthorisation of the Violence Against Women Act, which attempts to protect women from domestic violence, stalking, and date rape.

"She believes businesses have a right to refuse service to gay couples. She also believes they should not have the right to marry. These are not MY Tennessee values."

The National Republican Senate Committee issued a press release dismissing Swift's endorsement. "If you haven't heard, multimillionaire pop star Taylor Swift came down from her ivory tower to tell hardworking Tennesseans to vote for Phil Bredesen," the committee said.

Bredesen's campaign sent out a series of tweets on the endorsement.

".@VoteMarsha, look what you made her do. @taylorswift13 doesn't like your little games and she wants Tennesseans to know that you've been in the swamp long enough. It's time for some fresh air up in Washington," they tweeted.